1. Field of the Invention
The invention relates to oil well flow diverter apparatus and systems. In particular the invention is directed to apparatus for diverting well bore flow safely away from an oil rig where unbalanced well bore pressure in the annulus between the well bore and a drill string causes the flow rate to exceed a safe rate through the rig mud piping and control system.
2. Description of the Prior Art
When drilling an oil well, an initial large diameter bore is drilled to shallow depths. Protective drive or conductor pipe, typically thirty (30) inches in diameter, is secured in the shallow bore through which the drilling takes place. For offshore floating drilling a subsea riser extends from the drilling rig to the well-head at the sea floor. Flow diverters are typically provided below the rig floor and between the conductor pipe and the rotary table of the drilling rig. A flow diverter provides a means for controlling "kicks" of low pressure formation gas accumulations in the fluid of the subsea riser encountered in top hole drilling.
Prior diverter systems have been primarily of two types: the first includes a flow diverter assembly requiring different diameter packing inserts to accommodate different diameter tubular members; the second includes an annular blowout preventer placed above a vent line in which a valve is disposed to open when the annular blowout preventer is closed about the drill pipe or other object in the well bore in response to a "kick" in the annulus of the borehole.
In the first type of flow diverters, packer elements must be changed for different sized tubulars in the bore and are in general unable to close the borehole when no tubular is in the borehole to close about.
In the second type system the combined height of the annular blowout preventer and of the side outlets of the vent line below the annular blowout preventer may require excessive headroom under the rig floor. The combined height may be a disadvantage where rigs have limited height and transfer capabilities, because the assembled blowout preventer/side outlet assembly is advantageously moved and lowered through the rig rotary table in position below the rig floor.
An advantageous feature of the flow diverter apparatus to be described below is that while it provides apparatus that can pack about tubular or other goods in the well bore of varying diameters (or even completely close the well bore where no object is in the well bore) it also eliminates the need for vent line placement below the diverter apparatus.